High strength titanium base zirconium-aluminum alloy



United States Patent 3,114,632 HTGH STRENGTH TlTANIUM BASE ZIRCONIUM- ALUMINUM ALLOY Clayton D. Dickinson and Staniey Abkowitz, Warren, Ohio, and Ronaid J. Nyien, Chicago, Ill., asslguors, by mesne assignments, to National Distillers and Chemical Corporation, a corporation of Virginia No Drawing. Filed Oct. 14, 1959, Ser. No. 846,251 4 Claims. (Cl. 75-1755) The invention relates to titanium base alloys and more particularly to a titanium base alloy containing zirconium and aluminum; and this application is a continuation-1npart of our application Serial No. 744,071, filed June 24, 1958, now abandoned.

More particularly, the invention relates to a titanium alloy which has high elevated temperature strength, and exceedingly favorable strength and ductility properties at room temperature in the annealed condition.

From the standpoint of economics there has been an existing need for a titanium alloy which has high strength at elevated temperatures and exceedingly favorable stren th and ductility properties at room temperature in the annealed condition. That is to say, there has been a need for an alloy which displays the stated-properties but yet which can be manufactured from commercial titanium sponge such as 120 BHN sponge.

We have discovered that a Ti-12Zr-7Al alloy (constituent percentages by weight) has the stated desirable combined characteristics or properties.

Accordingly, it is a general object of the present invention to provide a new Ti-12Zr-7Al alloy characterized by having high strength and ductility in the annealed condition at room temperature as well as high elevated temperature strength accompanied when made from 120 BHN sponge by some ductility and lack of complete brittleness when heated to 1020 F. for 48 hours followed by air cooling.

Furthermore, it is an object of the present invention to provide a new Ti-12Zr-7Al alloy which has an ultimate tensile strength of about 90,000 p.s.i. and a yield strength at 0.2% offset of about 69,000 p.s.i. at 800 to 1000 F.

Also it is an object of the present invention to provide a new Ti-l2Zr-7Al alloy in which high ductility of elongation in 1'' may be retained after heating to 1020 F. for 48 hours followed by air cooling if made from selected low hardness commercial 90 BHN titanium sponge.

Also it is an object of the present invention to provide a new Ti-12Zr-7Al alloy which plastically deforms only about 53% when stressed at 45,000 p.s.i. for 150 hours at 1000 F, and which retains ductility of 6.3% elongation in /2" and 12.4% reduction in area after such creep exposure.

Moreover, it is an object or" the present invention to provide a new Ti-l2Zr-7Al alpha alloy which is weldable, and is very strong and ductile for room temperature applications and which may retain ductility of 10% elongation in 1" after exposure to 1020 F. for 48 hours followed by air cooling when made from selected low hardness commercial 90 BHN sponge.

Finally, it is an object of the present invention to provide a new Ti-l2Zr-7Al alloy having the combined stated properties and characteristics.

These and other objects and advantages apparent to those skilled in the art from the following description and claims may be obtained, the stated results achieved, and the described difficulties overcome by the discoveries, principles, compositions and alloys which comprise the present invention, the nature of which is set forth belowillustrative of the best mode in which applicants have 3,114,632 Patented Dec. 17, 1963 ice contemplated applying the princip1esand which are particularly and distinctly pointed out and set forth in the appended claims forming part hereof.

The alloys of the present invention may be prepared from either commercial titanium or high purity titanium. However, one of the advantages of the improved alloy is its ability to develop the room temperature properties indicated in making the alloy from commercial titanium such as titanium sponge having a hardness of 120 BHN. A typical analysis of 120 BHN sponge includes, in addition to titanium, 0.02% C, 0.01% N 0.10% 0 and 0.005% H A typical analysis of BHN sponge, which also may be used in making the improved alloy of the invention, includes in addition to titanium, .03% C, 009% N .020% O .0032% H and .03% Fe.

In practice, the alloy is preferably double melted by the electric arc process in a water-cooled copper crucible either in a vacuum or in an atmosphere such as argon, and the alloying elements are added to titanium sponge in the melt separately. Thus the aluminum may be added as pure aluminum shot, and the zirconium as pure zirconium sponge.

The alloy of the present invention after melting and casting may be processed in the usual manner and forged or hot rolled to form the desired semi-finished or finished product. For instance, where bars are produced, the ingots may be forged at say 2000 F. to 2100 F. to form billets and then hot rolled to form bars of the desired size, for example bars.

Table I below indicates the mechanical properties of the nominal composition Ti-12Zr-7Al alloy of the present invention made from BHN sponge forged at 2100" F and rolled at 1700 F. to form bars.

' Table 1 Y8, Elong R.A., Spec Heat Treatment UTS, 0.2% in 1" per- N o. k.s.i. 01f, percent k.s.i cent 1,700 F.1 hr.a.c 137 15.0 35. 4 1,700" F.1 hr.-a.c 150 137 16.0 35.1 l,700 F.2 hrs.a. 149 136 16.0 31. 3 1,700 F.2 hrs.a.c 150 137 14. 5 31. 9 1,700 F.2 hrs.a.c.; 153 139 5. 5 7. 8

1,020 F.48 hrs-21.0. 1,700 F.2 hrs.a.c.; 154 139 5.0 8. 6

1,020 F.-48 hrs.-a.c.

The Ti-12Zr-7Al alloy of Table I shows remarkably high room temperature strength as annealed for l or 2 hours and air cooled, of about 150,000 p.s.i. ultimate strength and 137,000 p.s.i. yield strength at 0.2% offset with 14.5 to 16% elongation in 1" (specimens 1, 2, 3 and 4).

When the alloy of Table I is heated to 1020 F. for 48 hours and air cooled, the strength is unaffected but its ductility is reduced though the alloy is not completely brittle, retaining 5% elongation in 1".

However, if the alloy is made from 90 BHN sponge, and annealed at 1700 F. for two hours and air cooled, it has an ultimate strength of 139,000 p.s.i., a yield strength at 0.2% offset of 122,000 p.s.i., elongation in one inch of 14.2% and reduction in area of 33%. When this alloy (90 BHN sponge) is heated to 1020 F. for 48 hours and air cooled it has an ultimate strength of 144,000 p.s.i., yield strength at 0.2% offset of 126,500 p.s.i., elongation in one inch of 10.2% and reduction in area of 23.8%.

Thus, by making the alloy of selected low hardness sponge, such as 90 BHN sponge, although the room temperature strength is reduced somewhat, the alloy retains 10% elongation in 1 ductility after exposure to high temperatures. Furthermore, when the alloy made from 90 BHN sponge is exposed to creep conditions, that is,

stressed at 45,000 p.s.i. for 150 hours at 1000 F., it has a measured permanent deformation of only 0.53 After creep exposure the alloy has an ultimate strength of 150,000 p.s.i., a yield strength at 0.2% offset of 129,000 p.s.i., elongation in A2" of 6.3% and reduction in area of 12.4%.

The improved alloy, in addition to having the combination of stated favorable properties, is weldable, is not difiicult to fabricate, and has outstanding oxidation resistance. Test bars which had been held at 1000 F. for 150 hours were only slightly oxidized, in many cases only stained, after exposure.

It is to be understood that in the foregoing table, where intended composition has been given, there may be some variation in actual composition determined by chemical analyses. Compositions are usually close to the nominal or intended composition but may vary slightly either way from the intended value, depending upon the ability to control the exact amount of alloying additions made.

The improved alloy of the present invention in combining high strength and favorable ductility properties at room temperature, ease of fabrication, Weldability and oxidation resistance provides a new material satisfying many room temperature applications, which may be manufactured from commercial 120 BHN titanium sponge; and also provides a material when made from selected low hardness 90 BHN sponge which has elongation in 1" or more ductility and lack of brittleness after exposure to 1020 F. for 48 hours and air cooling, along with high creep resistance.

In the foregoing description, certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes herein and are intended to be broadly construed.

Having now described the invention, the features, discoveries and principles thereof, the characteristics of the new alloy, and the new and useful results obtained; the new and useful compositions, combinations, products, discoveries and principles and reasonable mechanical equivalents thereof, obvious to those skilled in the art, are set forth in the appended claims.

We claim:

1. A titanium base alloy consisting of 12% Zr, 7% Al by weight and the balance titanium with incidental impurities, said alloy at room temperature as annealed having an ultimate tensile strength of 150,000 p.s.i., a yield strength at 0.2% offset of 137,000 p.s.i., elongation in 1" of from 14.5% to 16%, and reduction in area of from 31.3% to 35.1%.

2. A titanium base alloy consisting of 12% Zr, 7% Al by weight and the balance titanium with incidental impurities, said alloy being characterized when made from BHN sponge by 10.2% room temperature elongation in 1" after heating to 1020 F. for 48 hours followed by air cooling.

3. A titanium base alloy consisting of 12% Zr, 7% Al by weight and the balance titanium with incidental impurities, said alloy being characterized when made from 90 BHN sponge by 53% permanent deformation when stressed at 45,000 p.s.i. for 150 hours at 1000 F.

4. A titanium base alloy consisting of 12% Zr, 7% Al by weight and the balance titanium with incidental impurities; said alloy at room temperature as annealed having an ultimate strength of from 139,000 to 150,000 p.s.i., yield strength at 0.2% offset of from 122,000 to 137,000 p.s.i., elongation in 1" of from 14.2 to 16% and from 31.3% to 35.1% reduction in area; said alloy having from 5.0% to 10.2% elongation in 1" after heating to 1020 F. for 48 hours followed by air cooling when made from 90 to BHN sponge; and said alloy being characterized by having from 53% to .63% permanent deformation upon stressing at 45,000 p.s.i. for hours at 1000 F. when made from 90 to 120 BHN sponge.

References (Iited in the file of this patent UNITED STATES PATENTS 2,267,298 Dean Dec. 23, 1941 2 ,754,205 Jafree et al July 10, 1956 2,781,261 Kamlet Feb. 12, 1957 2,868,640 Butler Jan. 13, 1959 2,880,087 Jafiee Mar. 31, 1959 2,892,705 Jatfee et a1 June 30, 1959 

1. A TITANIUM BASE ALLOY CONSISTING OF 12% ZR, 7% AL BY WEIGHT AND THE BALANCE TITANIUM WITH INCIDENTAL IMPURITIES, SAID ALLOY AT ROOM TEMPERATURE AS ANNEALED HAVING AN ULTIMATE TENSILE STRENGTH OF 150,000 P.S.I., A YIELD STRENGTH AT 0.2% OFFSET OF 137,000 P.S.I., ELONGATION IN 1" OF FROM 14.5% TO 16%, AND REDUCTION IN AREA OF FROM 31.3% TO 35.1%. 